Machine holding fixture for machining composite laminates on a rotor blade

ABSTRACT

A holding fixture includes a first blade support assembly and a second blade support assembly. The second blade support assembly is spaced at a distance from the first blade support assembly and includes a base plate removably mounted to a milling machine, an adjustable conic support connectable to the base plate via a spacer block, and a blade adjustment assembly movable to control a pressure applied by the blade adjustment assembly.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.15/282,239 filed Sep. 30, 2016, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

Exemplary embodiments of the invention relate to rotary-wing aircraftand, more particularly, to a bond fixture for use during the manufactureor repair of a rotor blade of a rotary-wing aircraft.

Rotary wing aircraft include a plurality of main rotor blades coupled toa central hub. The rotor blades include aerodynamic surfaces that, whenrotated, create lift. The configuration of the main rotor blades,particularly the leading edge thereof, is selected to enhance rotorblade performance, for example to increase the hover and liftcapabilities of the rotary-wing aircraft. Rotor blades are subjected tohigh stresses and strains resulting from aerodynamic forces developedduring operation.

BRIEF DESCRIPTION OF THE INVENTION

According to one embodiment of the invention, a holding fixture includesa first blade support assembly and a second blade support assembly. Thesecond blade support assembly is spaced at a distance from the firstblade support assembly and includes a base plate removably mounted to amilling machine, an adjustable conic support connectable to the baseplate via a spacer block, and a blade adjustment assembly movable tocontrol a pressure applied by the blade adjustment assembly.

In addition to one or more of the features described above, or as analternative, in further embodiments the conic support includes at leastone pin receivable within a hollow interior of a blade spar of a rotorblade.

In addition to one or more of the features described above, or as analternative, in further embodiments the conic support includes two pinsreceivable within the hollow interior of the blade spar.

In addition to one or more of the features described above, or as analternative, in further embodiments the position of the pins may beadjusted to control a pressure applied by the pins to the blade spar tocouple the conic support to the blade spar.

In addition to one or more of the features described above, or as analternative, in further embodiments the holding fixture furthercomprises a contour support having a first support plate and a secondsupport plate. The second support plate is movable between a closedposition and an open position.

In addition to one or more of the features described above, or as analternative, in further embodiments an interior surface of both thefirst support plate and the second support plate is complementary to arotor blade such that when the second support plate is in the closedposition, the first support plate and the second support plate areoperable to apply a pressure to the rotor blade to restrict movement ofthe rotor blade relative to the first blade support assembly.

In addition to one or more of the features described above, or as analternative, in further embodiments the second support plate ispivotally coupled to the first support plate.

In addition to one or more of the features described above, or as analternative, in further embodiments the second support plate isdetachably coupled to the first support plate.

In addition to one or more of the features described above, or as analternative, in further embodiments the first blade support assemblyincludes a table and the contour support is mounted to an upper surfaceof the table.

In addition to one or more of the features described above, or as analternative, in further embodiments the contour support is connected toan upper surface of the base plate.

According to another embodiment, a method of machining a laminateattached to a surface of a rotor blade includes providing a firstassembly for supporting a first portion of the rotor blade and providinga second assembly for supporting a second portion of the rotor blade.The second assembly is spaced apart from the first assembly and includesa base plate. The base plate is coupled to a milling machine. A conicsupport is attached to a root end of the rotor blade. The conic supportis mounted to the base plate. The rotor blade is positioned relative tothe first assembly and the second assembly such that movement of therotor blade is restricted and a first surface of the rotor bladeincluding a first laminate is facing upwardly. The blade adjustmentassembly is operated such that a block of the blade adjustment assemblyis nested against an underside of the rotor blade. The first laminate ismachined to remove a desired portion.

In addition to one or more of the features described above, or as analternative, in further embodiments positioning the rotor blade relativeto the first assembly and the second assembly includes enclosing therotor blade within a first contour support associated with the firstassembly and a second contour support associated with the secondassembly.

In addition to one or more of the features described above, or as analternative, in further embodiments attaching the conic support to theroot end of the rotor blade includes inserting a plurality of supportpins extending from the conic support into a blade spar of the rotorblade and adjusting the plurality of support pins to apply a pressure toopposite sides of the blade spar.

In addition to one or more of the features described above, or as analternative, in further embodiments mounting the conic support to thebase plate includes fastening the conic support to a spacer blockextending from an upper surface of the base plate.

In addition to one or more of the features described above, or as analternative, in further embodiments including removing the rotor bladefrom the holding fixture, repositioning the rotor blade relative to thefirst assembly and the second assembly such that movement of the rotorblade is restricted and a second surface of the rotor blade including asecond laminate is facing upwardly, operating the blade adjustmentassembly such that a block of the blade adjustment assembly is nestedagainst an underside of the rotor blade, and machining the secondlaminate to remove a desired portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of an example of a rotary wing aircraft;

FIG. 2 is a perspective view of an example of a rotor blade of a rotarywing aircraft;

FIG. 3 is a perspective view of a holding fixture for supporting a rotorblade during a machining operation according to an embodiment;

FIG. 4 is a side view of the holding fixture of FIG. 3 according to anembodiment;

FIG. 5 is a top view of the second assembly of the holding fixtureaccording to an embodiment;

FIG. 6 is a side view of the second assembly of the holding fixtureaccording to an embodiment;

FIG. 7 is a perspective view of the root end of the rotor blade engagedwith the second assembly of the holding fixture according to anembodiment;

FIG. 8 is an end view of the root end of the rotor blade engaged withthe second assembly of the holding fixture of FIG. 7 according to anembodiment;

FIG. 9 is an exploded perspective view of the second contour supportaccording to an embodiment;

FIG. 10 is an end view of the second contour support according to anembodiment; and

FIG. 11 is a method of machining a composite laminate of a rotor bladeaccording to an embodiment.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically illustrates a rotary-wing aircraft 10 having a mainrotor system 12. The aircraft 10 includes an airframe 14 having anextending tail 16 which mounts a tail rotor system 18, such as ananti-torque system for example. The main rotor assembly 12 is drivenabout an axis of rotation A through a main gearbox (illustratedschematically at T) by one or more engines E. The main rotor system 12includes a plurality of rotor blade assemblies 20 mounted to a rotor hubassembly H. Although a particular helicopter configuration isillustrated and described in the disclosed non-limiting embodiment,other configurations and/or machines, such as high speed compoundrotary-wing aircraft with supplemental translational thrust systems,dual contra-rotating, coaxial rotor system aircraft, turbo-props,tilt-rotors, and tilt-wing aircraft are also within the scope of theinvention.

Referring to FIG. 2, each rotor blade assembly 20 of the rotor assembly12 generally includes a root section 22, an intermediate section 24, atip section 26, and a tip cap 28. Each rotor blade section 22, 24, 26,28 may define particular airfoil geometries to tailor the rotor bladeaerodynamics to the velocity increase along the rotor blade span. As,illustrated, the rotor blade tip section 26 may include an anhedral form(not shown); however, any angled or non-angled forms such as cathedral,gull, bent, and other non-straight forms are within the scope of thepresent invention. The anhedral form (not shown) as defined herein mayinclude a rotor blade tip section 26 which extends at least partiallyout of a plane defined by the intermediate section 24.

The rotor blade sections 22-28 define a span R of the main rotor bladeassembly 20 between the axis of rotation A and a distal end 30 of thetip cap 28 such that any radial station may be expressed as a percentagein terms of a blade radius x/R. The rotor blade assembly 20 defines alongitudinal feathering axis P between a leading edge 32 and a trailingedge 34.

A holding fixture 40 for holding the rotor blade 20 in position during amilling operation is illustrated in FIGS. 3-10. The holding fixture 40includes a first assembly 44 for supporting a central or outboardportion of the rotor blade 20 and a second assembly 42 for supportingthe inboard end 22 of the rotor blade 20. The first assembly 44 includesa movable table 46 having a generally planar upper surface 48. A firstcontour support 50 mounted to the upper surface 48 of the movable table46 includes a stacked first support plate 52 and a second support plate54. In an embodiment, the first support plate 52 and the second supportplate 54 are pivotally coupled adjacent a first end such that the secondsupport plate 54 is movable relative to the first support plate 52between an open position and a closed position. The inner surface ofboth the first support plate 52 and the second support plate 54 has acontour corresponding to an adjacent surface of the rotor blade 20. As aresult, the rotor blade 20 is receivable within the contour support 50when the second support plate 54 is in an open configuration. Further,when the second support plate 54 is in the closed position, the firstcontour support 50 applies a pressure to the surface of the rotor blade20 to prevent movement thereof relative to both the contour support 50and the table 46.

The second assembly 42 includes a base plate 60 adapted to mount, suchas with one or more fasteners (not shown) to a corresponding surface ofa milling machine (not shown). When the base plate 60 is coupled to themilling machine, an upper surface 62 of the base plate 60 may, but neednot be substantially flush with the upper surface 48 of the table 46.The base plate 60 is spaced away from the leading edge of the table 46by a predetermined distance associated with the rotor blade 20.

A second contour support 64 configured to mount to the upper surface 62of the base plate 60 similarly includes a stacked first support plate 66and a second support plate 68. In an embodiment, the first support plate66 and the second support plate 68 are pivotally coupled adjacent afirst end such that the second support plate 68 is movable relative tothe first support plate 66 between an open position and a closedposition. Alternatively, the second support plate 68 may detachablycouple to the first support plate 66. The inner surface of the first andsecond support plates 66, 68 is contoured to match an adjacent surfaceof the rotor blade 20, near the root or inboard end. As a result, whenthe second support plate 68 is substantially aligned with the firstsupport plate 66 to define a chamber 70 within which the rotor blade 20is received (see FIG. 10), the second contour support 64 applies apressure to the surface of the rotor blade 20 to prevent movementthereof relative to the contour support 64 and the base plate 60.

Located near the first end 72 of the base plate 60 is a block spacer 74configured to cooperate with a conic support 76. When the conic support76 is coupled to the spacer 74, the conic support 76 is substantiallyaligned with the blade spar 36 (FIG. 7) of the adjacent rotor blade 20.The conic support 76 includes at least one support pin 78 receivablewith a hollow interior of the rotor blade spar 36. In the illustrated,non-limiting embodiment, the conic spar 76 includes two support pins 78.An adjustment assembly 80 associated with the two support pins 78 isoperable to adjust the relative position of the two support pins 78. Forexample, the adjustment assembly 80 includes a wheel 82 that whenrotated in a first direction moves the support pins 78 towards oneanother and when rotated in a second direction moves the support pins 78away from one another. To couple the conic support 76 to the rotor blade20, the support pins 78 are adjusted to apply a pressure to the opposingsurfaces of the interior of the blade spar 36.

A blade adjustment assembly 84 is coupled to or integrally formed withthe base plate 60. In an embodiment, the blade adjustment assembly 84 ispositioned between the block spacer 74 and the second contour support64. The blade adjustment assembly 84 is operable to adjust the height ofa spacer 86 disposed between the base plate 60 and an adjacent surfaceof the rotor blade 20. The spacing provided by the blade adjustmentassembly 84 is particularly important after a laminate located on afirst side of the rotor blade 20 has been machined. The spacer 86 may beadjusted to compensate for the height of the laminate that was removedwhen the rotor blade 20 is repositioned within the fixture 40 formachining of a laminate located on a second opposite side of the rotorblade 20. In the illustrated, non-limiting embodiment, the bladeadjustment assembly 84 includes a slidable block 86 engaged with a ramp88. A knob 90 connected to the ramp 88 may be manipulated, such aspushed or pulled longitudinally or rotated for example, to adjust theslope of the ramp 88 and control the distance between the upper surface62 of the base plate 60 and the upper surface of the block 86. It shouldbe understood that the blade adjustment assembly 84 illustrated anddescribed herein is intended as an example only, and that otherassemblies configured to control the position of the rotor blade 20relative to the upper surface 62 of the base plate 60 are alsocontemplated herein.

With reference now to FIG. 11, a method of machining a compositelaminate of a rotor blade 20 includes connecting the base plate 60 tothe milling machine (not shown) at a desired position relative to thecenter line of the cutter, as shown in block 102. The first supportplate 66 of the second contour support 64 is coupled to the uppersurface 62 of the base plate 60 in block 104, and the first assembly 44is positioned at a desired distance from the base plate 60 of the secondassembly 42 and is aligned therewith using a laser, block 106. In block108, the first contour support 50 is mounted to the upper surface 48 ofthe first assembly 44 and is oriented such that the second support plate54 is in an open position relative to the first support plate 52. Inblock 110, the conic support 76 is installed into the root end 22 of theblade 20 and is tightened to ensure that the conic support 76 remainsnested within the root end.

The rotor blade 20 is then positioned relative to the first assembly 44and the second assembly 42 in block 112 such that a first side of therotor blade 20 having a first laminate is facing upward. Positioning ofthe rotor blade 20 relative to first assembly 44 includes inserting therotor blade 20 within the first support plate 52 of the first contoursupport 50 and rotating the second support plate 54 such that the rotorblade 20 is substantially enclosed by the first contour support.Similarly, positioning of the rotor blade 20 relative to the secondassembly 42 includes positioning the conic support 76 onto the spacerblock 74 and securing the conic support thereto. In block 114, thesecond support plate 68 of the second contour support 64 is coupled tothe first support plate 66 and in block 116, the blade adjustmentassembly 84 is operated until the block 86 is nested against thelaminate located on the underside of the rotor blade 20, closest to theupper surface 62 of the base plate 60. In block 118, the milling machine(not shown) is then operated to remove a desired portion of the firstlaminate. The blade 20 may be removed from the holding fixture 40 via areverse order and may be reinstalled following the same steps with thesecond side of the rotor blade 20 and the second laminate facing upward.When installing the blade 20 with the second side facing upward, afterthe first laminate has been machined, the position of the sliding block86 of the blade adjustment assembly 84 will be in a different locationdue to the reduced thickness of the first laminate, and there istherefore the need for an increased spacer height.

The holding fixture 40 illustrated and described herein allows the rotorblade to be held stationary in a fixed location during both themanufacture of a new rotor blade 20 and the repair of an existing rotorblade 20.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

What is claimed is:
 1. A method of machining a laminate attached to asurface of a rotor blade comprising: providing a first assembly forsupporting a first portion of the rotor blade; providing a secondassembly for supporting a second portion of the rotor blade, the secondassembly being spaced apart from the first assembly and including a baseplate; coupling the base plate to a milling machine; attaching a conicsupport to a root end of the rotor blade; mounting the conic support tothe base plate; positioning the rotor blade relative to the firstassembly and the second assembly such that movement of the rotor bladeis restricted and a first surface of the rotor blade including a firstlaminate is facing upwardly; operating a blade adjustment assembly suchthat a block of the blade adjustment assembly is nested against anunderside of the rotor blade; and machining the first laminate to removea desired portion.
 2. The method according to claim 1, whereinpositioning the rotor blade relative to the first assembly and thesecond assembly includes enclosing the rotor blade within a firstcontour support associated with the first assembly and a second contoursupport associated with the second assembly.
 3. The method according toclaim 1, wherein attaching the conic support to the root end of therotor blade includes inserting a plurality of support pins extendingfrom the conic support into a blade spar of the rotor blade andadjusting the plurality of support pins to apply a pressure to oppositesides of the blade spar.
 4. The method according to claim 1, whereinmounting the conic support to the base plate includes fastening theconic support to a spacer block extending from an upper surface of thebase plate.
 5. The method according to claim 1, further comprising:removing the rotor blade from the holding fixture; repositioning therotor blade relative to the first assembly and the second assembly suchthat movement of the rotor blade is restricted and a second surface ofthe rotor blade including a second laminate is facing upwardly;operating the blade adjustment assembly such that a block of the bladeadjustment assembly is nested against an underside of the rotor blade;and machining the second laminate to remove a desired portion.